Structural dynamics of a mobile substation during transport

Mobile substations can be defined as completely equipped electrical substations. There is a lack of existing scientific basis in the mechanical design of the structural components of the mobile substation. In concrete there are no capabilities to determine the dynamic behavior during transport and service conditions. Improper dimensioning of the structures results in an important degree of mechanical failures during transport. The dynamic response of structures on a mobile substation to transport motions depends on their strength of construction, ductility, and dynamic properties. Lightly damped structures that have one or more natural modes of oscillation within the frequency band of transport excitations can experience considerable amplification of both the forces and deflections. Thus, items of mobile substation equipment whose natural frequencies lie in the normal frequency range of transport motion are particularly vulnerable to damage and fatigue. Therefore we are interested in analyzing the natural frequencies, damping ratios (modal parameters) and level of accelerations of those components. In this paper it will be shown how above parameters can be retrieved from a road test on a mobile substation and be applied to develop adequate design rules and design tools as well as recommendations in order to guarantee the mechanical integrity of mobile substations during transport and service conditions. Finally the influence of conductor cables on the dynamic behavior of interconnected equipment will briefly be discussed.